The Longest Day

https://www1.zoechip.com/movie/the-longest-day-17885

In 1944, the U.S. Army and Allied forces plan a huge invasion landing in Normandy, France. Despite bad weather, General Dwight D. Eisenhower gives the okay and the Allies land at Normandy. General Norma Cota travels with his men onto Omaha Beach. With much effort, and lost life, they get off the beach, traveling deep into French territory. The German military, due to arrogance, ignorance and a sleeping Adolf Hitler, delay their response to the Allied landing, with crippling results.

From IMDB:

Classic WWII Film!!
The Longest Day (1962) - CO-Directors: Ken Annakin & Andrew Morton Everyone knows this was producer Darryl F. Zanuck's baby and it earns its place in cinema history as one of those epic style movies that treats its subject matter with the most serious of attitudes. Obviously a war is no laughing matter but, for better or worse, movies tend to simplify logistics while highlighting emotional chords, such as bravery and homemade apple pie. Zanuck, however, wanted the audience to understand the scope and grandeur of an enterprise like D-Day.
Utilizing a cast of thousands, half of which seemed to be cameo appearances by major stars of the day, Zanuck presents on wide screen all the action and turmoil that surrounded this turning point of WW II. The ever-fighting Republican John Wayne is there, along with Democrat Henry Fonda, tough guy Bob Mitchum, brooding Richard Burton, sexy Sean Connery and pit bullish Rod Steiger. Still for my money, one of the best landing on the beach scenes ever filmed. Sorry Mr.Spielberg. (B&W)